Description (provided in specific aims by applicant): Our long term goal is to understand how nonmuscle cells move and divide. Actin and actin motors provide the driving force for nonmuscle cell motility and cytokinesis, and a variety of actin-binding proteins regulate this process. However, the manner in which actin-binding proteins accomplish this is poorly understood. My major interest has been in the role of the tropomyosin isoforms and the proteins that interact with the tropomyosins, including caldesmon, tropomodulin, Endostatin and myosin Va. In the next Program period, I will continue to explore how these molecules ineract to effect cell motility and cytokineses. This project aims to study the roles of tropomyosin isoforms and their interacting proteins in regulating the motility and cytokinesis of nonmuscle cells. These proposed studies will combine molecular, biochemical and cell biological approaches together with computer-assisted reconstruction and motion analysis to investigate the functions of caldesmon phosphorylation sites, tropomyosin isoforms, tropomyosin interactions with tropomodulin and with endostatin, and functions of myosin Va.